There is a lot of great info here. However, the app is buggy. First/last frost dates were incorrect for my area, which causes incorrect planting dates. Although frost dates can be adjusted in app settings, the dates change back to the incorrect ones every time the app is closed and re-opened. Disabling location services in the Privacy menu fixes this on the iPhone version, but the iPad version provides no way to disable location services.
Also, the app takes forever to open on the iPad.
A potentially very useful app that is marred by annoying interface issues.
CosmicDrifter about When To Plant